Ethanol fermentation methods and systems

ABSTRACT

Methods and systems for purifying feedstock-to-ethanol fermentation products are disclosed. The methods include the use of a solvent in the form of a supercritical fluid or liquid gas such as supercritical CO2 or liquid CO2 to dry fermentation beer solids, and/or to extract oil, ethanol, or ethanol and oil from fermentation beer or mixtures derived therefrom. Systems include a separations reactor having a first portion defined by walls that are impermeable to fermentation beer liquids joined to a second portion defined by walls that are impermeable to fermentation beer liquids by a third portion defined by walls that are permeable to fermentation beer liquids and impermeable to fermentation beer solids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/844,898, having a filing date of Jul. 11, 2013. This provisionalapplication is herein incorporated by reference in its entirety.

FIELD

This specification relates to ethanol production processes, for examplecellulose-based feedstock-to-ethanol conversion processes, starch-basedfeedstock-to-ethanol conversion processes, such as corn-to-ethanolproduction processes, and systems implementing such processes. Thisspecification also relates to methods of purifying fermentationproducts, processes, and methods for extracting ethanol produced inethanol fermentation processes, as well as systems implementing suchprocesses.

BACKGROUND

Ethanol can be produced from grain-based feedstocks, cellulosicfeedstocks, and other plant material. In a conventional ethanol plantproducing ethanol from corn, corn kernels are processed to separate thestarch-containing material from other matter. The starch-containingmaterial is then slurried with water and liquefied to facilitatesaccharification and fermentation. The product of fermentation is beer,which comprises a liquid component including ethanol and water and asolids component including unfermented particulate matter.

According to a typical process used at conventional ethanol plants, theliquefaction of the starch-containing feedstock is done by ‘cooking’ theslurry at a temperature at or near the boiling point of water (e.g. inthe range of 60-80 degrees C. or greater). According to an alternativeprocess, developed and implemented by POET Research LLC, the assignee ofthe present application, and described for example in U.S. Patent Pub.No. 2005/0239181, raw starch may be converted and fermented without‘cooking’ or liquefaction.

In a conventional ethanol plant, the fermentation beer product mayundergo a distillation process to produce ethanol and stillage. Thestillage, or wet solids, can be dried into distillers dried grains, anoperation in which water is removed from the solids, typically in agas-fired dryer.

SUMMARY

In some embodiments, the present disclosure relates to methods andsystems for purifying fermentation products, for example as part of anoverall feedstock-to-ethanol fermentation conversion process.

In some embodiments, the methods and systems for purifying fermentationproducts relates to the use of a novel solvent as regards ethanolfermentation processes to separate the liquids component of fermentationbeer, which liquids component includes one or more of ethanol, oil, andwater, from the solids component of fermentation beer.

In some embodiments, the methods and systems for purifying fermentationproducts relates to the use of the novel solvent to dry the solidscomponent of fermentation beer. The drying methods and systems can beimplemented before or after beer distillation.

In some embodiments, the methods and systems for purifying fermentationproducts relates to the use of the novel solvent to extract oil, extractoil and ethanol, and/or extract ethanol from other process components.The extraction methods and systems can be implemented anywhere duringthe process flow in which it may be desirable to separate ethanol fromoil and/or other process components, or to separate ethanol and oil fromother process components, or to separate oil from other processcomponents.

In some embodiments, the methods for separating the liquids component offermentation beer from the solids component of fermentation beer involvedisplacing the liquids portion from the solids portion with a solventchosen from a supercritical fluid and liquid gas. In some embodiments,the solvent has a lighter density than ethanol, for example the solventis supercritical CO2 or liquid CO2. In some embodiments, displacinginvolves contacting the fermentation beer with the solvent in anextractor resulting in a solids stream including solvent and the solidscomponent and a liquids stream including solvent and the liquidscomponent; and, removing the solids stream from the extractor at a firstport and liquids stream from the reactor at a second port. In furtherembodiments, displacing involves: flowing the solvent through a firstend of a reactor having a length of walls segmented into a first lengthof impermeable walls that are impermeable to the liquids componentseparated from a second length of impermeable walls that are impermeableto the liquids component by a first length of permeable walls that arepermeable to the liquids component, through the first impermeable lengthof walls toward the permeable length of walls; flowing the fermentationbeer into a second end of the reactor through the second length ofimpermeable walls toward the permeable length of walls, resulting in thesolids stream flowing out the extractor at a first port located in thefirst end of the reactor and the liquids stream flowing out of thereactor through the permeable length of walls. In some embodiments, themethods also involve removing solvent from the solids stream, removingsolvent from the liquids stream, or both by converting the solvent togas.

In some embodiments, the methods of drying beer solids involves exposinga first mixture comprising a liquids portion and a beer solids portionto a solvent under a first set of conditions in which the solvent is inthe form of a supercritical fluid or a liquid gas, displacing theliquids portion of the first mixture with the solvent to form a secondmixture including the beer solids portion and the solvent; and, removingthe solvent from the second mixture. In some embodiments, the firstmixture is fermentation beer. In some embodiments, the first mixture iswhole stillage. In some embodiments, the first mixture is wet cake. Infurther embodiments, removing the solvent involves exposing the secondmixture to at least a second set of conditions resulting in the solventconverting to a gas, and venting the resultant gas. In yet furtherembodiments, exposing the second mixture to at least a second set ofconditions comprises exposing the second mixture to successively lowerpressure conditions, and venting comprises venting any resulting gasafter each successive lower pressure condition. In yet furtherembodiments, the methods also include capturing the vented gas andrecompressing the vented gas into a supercritical fluid or liquid gas.

In some embodiments the methods of extracting at least one of oil andethanol involves exposing a first mixture comprising at least one of oiland ethanol and at least one other component to a solvent in the form ofa supercritical fluid or liquid gas under a first set of conditions inwhich at least one of the oil and ethanol solubilizes in the solvent toform a second mixture; separating the second mixture from the at leastone other component; and, removing the solvent from the second mixture.In some embodiments, the first mixture is a slip stream derived from afermentation reactor. In some embodiments, the first mixture is afermentation beer. In some embodiments, the first mixture is afermentation beer after separating out beer solids. In some embodiments,the solvent is supercritical CO2 or liquid CO2 and the first set ofconditions is conditions of temperature and pressure in which ethanolbut not oil solubilizes in the solvent. In some embodiments, the firstset of conditions is conditions of temperature and pressure in whichethanol and oil solubilize in the solvent, and removing the solventinvolves: reducing the pressure sufficiently to separate the oil leavingbehind a second mixture comprising ethanol and solvent, separating theoil from the second mixture, and thereafter reducing the pressuresufficiently to convert the solvent to gas. In some embodiments,additional purification steps are performed to separate water, which mayhave been extracted with the ethanol, from the ethanol.

In some embodiments, the systems include a separations reactorconfigured for use in conjunction with, or configured for integrationinto, a feedstock-to-ethanol production facility, wherein theseparations reactor is suitable for use at conditions supporting asolvent (for example CO2) in a supercritical fluid form, in a liquid gasform, or both; and the separations reactor includes one or more inputsthrough which a first mixture chosen from a fermentation beer and amixture derived therefrom is introduced into the separations reactor andthrough which the solvent is introduced into the separations reactor,and one or more outputs through which separated components of thefermentation beer or mixture derived therefrom are removed from theseparations reactor. In some embodiments, the systems further include asolvent in supercritical form or liquid gas form.

In some embodiments, the systems include a feedstock-to-ethanolfermentation production facility; a solvent in supercritical fluid formor liquid gas form; a separations reactor integrated into thefermentation production facility, wherein the separations reactor issuitable for use at conditions supporting the solvent in a supercriticalfluid form, in a liquid gas form, or both; and the separations reactorincludes one or more inputs through which a first mixture chosen from afermentation beer and a mixture derived therefrom is introduced into theseparations reactor and through which the solvent is introduced into theseparations reactor, and one or more outputs through which separatedcomponents of the fermentation beer or mixture derived therefrom areremoved from the separations reactor.

In some embodiments, the separations reactor (for example of any of theabove-referenced systems) has a first impermeable portion joined to asecond impermeable portion by a third permeable portion, wherein thefirst impermeable portion and second impermeable portions are defined bywalls that are impermeable to liquids in the first mixture and the thirdpermeable portion is defined by walls that are permeable to liquids inthe first mixture; the one or more inputs is a first input located inthe first impermeable portion for introducing solvent into the reactorand a second input located in the second impermeable portion forintroducing the first mixture into the reactor; and, the one or moreoutputs is a first output located in the first impermeable section forremoving solids in the first mixture from the separations reactor and asecond output which is the permeable section. In further embodiments,the separations reactor also comprises a casing with an integral portaround the permeable section for capturing the liquids leaving thereactor through the permeable portion and directing them to a next partof the ethanol facility. In further embodiments, the first mixture isfermentation beer, the solids are beer solids and the liquids are beerliquids. In further embodiments, the separations reactor isvertically-oriented with the first impermeable portion being a top endof the reactor and the second impermeable portion being a bottom end ofthe reactor. In some embodiments, the systems also include an evaporatorin fluid communication with the first output, and which evaporator hasone or more discharge outlets for releasing gas produced when conditionsin the evaporator are set consistent with the solvent converting to agas phase. In some embodiments, the systems further comprise acompressor in fluid communication with the evaporator for recompressinggas discharged from the evaporator and means for recirculating therecompressed gas back into the separations reactor.

The identified embodiments are exemplary only and are thereforenon-limiting. The details of one or more non-limiting embodimentsaccording to the disclosure are set forth in the accompanying drawingsand the descriptions below. Other embodiments according to thedisclosure should be apparent to those of ordinary skill in the artafter consideration of the present disclosure.

DESCRIPTION OF DRAWINGS

FIG. 1 is a process flow diagram of an embodiment of a method accordingto this disclosure.

FIG. 2 is process flow diagram of an embodiment of afeedstock-to-ethanol fermentation process in which the method of FIG. 1may be integrated.

FIG. 3 is a schematic illustration of an embodiment of a separationsreactor in which certain methods according to this disclosure may beimplemented.

DETAILED DESCRIPTION I. Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this disclosure belongs. In the event that there isa plurality of definitions for a term herein, those in this sectionprevail unless stated otherwise.

Where ever the phrases “for example,” “such as,” “including” and thelike are used herein, the phrase “and without limitation” is understoodto follow unless explicitly stated otherwise.

The terms “comprising” and “including” and “involving” (and similarly“comprises” and “includes” and “involves”) are used interchangeably andmean the same thing. Specifically, each of the terms is definedconsistent with the common United States patent law definition of“comprising” and is therefore interpreted to be an open term meaning “atleast the following” and also interpreted not to exclude additionalfeatures, limitations, aspects, etc.

The term “about” is meant to account for variations due to experimentalerror or to permit deviations from the measurements that don'tnegatively impact the intended purpose. The term “substantially” ismeant to permit deviations from the descriptive term that don'tnegatively impact the intended purpose. All measurements or numbers areimplicitly understood to be modified by the word about, even if themeasurement or number is not explicitly modified by the word about. Alldescriptive terms are implicitly understood to be modified by the wordsubstantially, even if the descriptive term is not explicitly modifiedby the word substantially.

Where ever the terms “a” or “an” are used, “one or more” is understoodunless explicitly stated otherwise or such interpretation is nonsensicalin context.

Where ever the text refers to displacing/extracting/separating/ventingof one component or components from another component or components, itis understood that the action may not result in completedisplacement/extraction/separation/venting of the components. Forexample, where ever the text refers to displacing the liquids fractionfrom the solids fraction of the wet solids, or extracting the liquidsfraction from the solids fraction of the wet solids, or separating theliquids fraction from the solids fraction, it is understood that thephase “at least a portion of” modifies the displaced/extracted/separatedfraction regardless of whether or not that phrase explicitly appears inthe text, unless specifically stated otherwise. In other words,“displacing the liquids fraction from the solids fraction” means:“displacing at least a portion of the liquids fraction from the solidsfraction.”

“Liquid gas” refers to a substance that is in the gas phase at roomtemperature and pressure but may be converted to a liquid phase and usedas a solvent in processes according to this disclosure.

The term “purify” and the like does not mean 100% pure but rather onlythat the target product is not part of the same original mixture inwhich it is found. Thus, for example, “purifying fermentation products”means that at least a portion of the target product or products isseparated from the fermentation mixture, but after separation mayinclude other components from the fermentation mixture as well as thetarget product.

The present disclosure relates to methods and systems for purifyingfermentation products, for example as part of an overallfeedstock-to-ethanol fermentation conversion process, such as acorn-to-ethanol fermentation conversion process. Traditionally, the mainproducts of the feedstock-to-ethanol fermentation process are ethanoland beer solids, which can be Dried Distiller's Grain (DDG) in the caseof corn-to-ethanol fermentation processes. The products aretraditionally derived from the fermentation beer throughenergy-intensive distillation and drying systems. Fermentation beer canalso include oil and water.

In some embodiments, the present disclosure provides approaches toseparating out one or more of the products such as ethanol and driedbeer solids (e.g. DDG) from the fermentation beer, directly orindirectly, in a more energy efficient manner than the traditionaldistillation and drying approaches described in the background section.“Directly” means the methods and systems are integrated withfermentation itself, whereas “indirectly” means the methods and systemsare applied downstream of fermentation. For example, in some directembodiments, a novel solvent is used to displace the liquids fraction ofthe fermentation beer from the solids fraction, resulting in a firstmixture of solvent and ethanol (and potentially oil and water) and asecond mixture of solvent and beer solids. As another example, in somedirect embodiments, a novel solvent contacts a slip stream taken fromthe fermenter during fermentation. In some indirect embodiments, a novelsolvent is used for separation of ethanol or drying of solids afterfermentation and distillation.

In some embodiments, the methods and systems for purifying fermentationproducts relates to the use of a novel solvent as regards ethanolfermentation processes to separate the liquids component of fermentationbeer from the solids component of fermentation beer. In someembodiments, the methods and systems for purifying fermentation productsrelates to the use of the novel solvent to dry the solids component offermentation beer. The drying methods and systems can be implementedbefore or after beer distillation.

In some embodiments, the methods and systems for purifying fermentationproducts relates to the use of the novel solvent to extract oil, extractoil and ethanol, and/or extract ethanol from other process components.The extraction methods and systems can be implemented anywhere duringthe process flow in which it may be desirable to separate ethanol fromother process components, or to separate ethanol and oil together fromother process components, or to separate oil from other processcomponents. As a person of skill may understand from reading thisspecification, water may be extracted along with ethanol. Accordingly,some embodiments involve additional purification steps to separate waterand ethanol. Any purification scheme known in the art to separate waterand ethanol may be used, such as for example distillation. Alternativelyor in addition, water may be separated from ethanol using the novelsolvent described herein, in one or more than one iterative separationstep.

In general, the methods and systems of this disclosure relate to the useof a novel solvent as regards feedstock-to-ethanol fermentationprocesses. The novel solvent is a substance in supercritical fluid orliquid gas form, which in some embodiments is used as a “displacent” todisplace the liquids component of a mixture from the solids component ofa mixture (such as to displace the liquids component of fermentationbeer from the solids component of fermentation beer), in someembodiments the novel solvent is used to dry the solids component offermentation beer, and in other embodiments is used an extractionsolvent (“extractant”) to remove oil, ethanol, or oil and ethanol fromother process components. In some embodiments, the solvent is chosenfrom substances which under operation conditions (e.g. under conditionsin which it is used as a displacent or as an extractant) are insupercritical or liquid gas form.

In some embodiments, the solvent is a supercritical fluid. In someembodiments, the substance which is used in supercritical fluid form ischosen from any substance that has a supercritical phase at temperaturesabove the freezing temperature of the liquid component and correspondingpressures which result in the supercritical form. In some embodiments,the substance which is used in supercritical form is chosen from anysubstance that has a supercritical phase at temperatures ranging fromgreater than 32 degrees F., or greater than 40 degrees F., or greaterthan 45 degrees F., and corresponding pressures which result In thesupercritical form. In some embodiments, the supercritical fluid ischosen such that the amount of energy required to convert it to a gasand thereby dry an amount of wet solids derived from a fermentation beeris favorable (less than) the amount of energy required to drive offwater (boil off water) from the same amount of wet solids derived from afermentation beer. For example, in some embodiments, the solvent can besupercritical CO2 or supercritical nitrogen. In embodiments whereinsupercritical CO2 is the solvent, it can be sourced from CO2 produced inthe feedstock-to-ethanol conversion process.

In some embodiments, the solvent is a liquid gas. In some embodiments,the solvent is chosen from any liquid gas that has a heat ofvaporization less than that of water. In some embodiments, the liquidgas is chosen from any substance that has a liquid phase at temperaturesbelow the critical point and pressures sufficient to hold the gas inliquid phase without solidifying the gas. For example, in someembodiments, the solvent can be a substance that is in liquid gas format about 10 degrees C. and 50 bar. In some embodiments, the liquid gasis chosen such that the amount of energy required to convert it to a gasand thereby dry an amount of wet solids derived from a fermentation beeris favorable (less than) the amount of energy required to drive offwater (boil off water) from the same amount of wet solids derived from afermentation beer. In some embodiments, the liquid gas is derived from acompound that is in liquid phase at temperatures at or below the boilingpoint of water at operational pressure, for example below the boilingpoint of water at atmospheric pressure. For example, in someembodiments, the solvent can be liquid CO2. In embodiments whereinliquid CO2 is the solvent, it can be sourced from CO2 produced in thefeedstock-to-ethanol conversion process.

Referring now to the figures, wherein like reference numerals indicatelike elements, FIG. 1 is process flow diagram of an embodiment of amethod according to this disclosure. As shown, fermentation beer 20 andsolvent 23 are brought into contact with one another, for example in areactor 10 resulting in two product streams: a liquids product stream 16and a solids product stream 15. The liquids product stream 16 maycontain (among other things) ethanol, oil, water and solvent. The solidsproduct stream 15 may contain (among other things) beer solids andsolvent. As is understood, separations may be imperfect and consequentlythe beer liquids stream may include some beer solids, and the beersolids stream may include some liquids such as ethanol.

FIG. 2 is a process flow diagram of an embodiment of afeedstock-to-ethanol conversion process in which the method of FIG. 1may be integrated. As a person of skill understands from reading thisdisclosure, the conversion process of FIG. 2 is only one conversionprocess into which methods according to the disclosure may beintegrated. Also as a person of skill understands, not all steps shownin FIG. 2 are necessary, and some similar conversion processes mayinclude additional or alternative steps, some of which are identifiedbelow.

Turning back to FIG. 2, as shown, feedstock 12 is initiallyprepared/fractionated 24 for downstream saccharification andfermentation, wherein for example corn kernels are separated intonon-fermentable solids 25 (e.g. germ and fiber) and fermentable solids(e.g. endosperm). Once the endosperm has been separated from thenon-fermentable solids, it may be ground and directed into asaccharification process 26. Separation and grinding of endosperm mayalso be conducted in an integrated process. Saccharification process 26may be a ‘cooked’ or cold process depending, for example, on the choseninput enzymes, and results in converting starches within the groundendosperm being converted to sugars. A fermentation slurry may bedirected from saccharification process 26 to fermentation process 28.

Fermentation process 28 may also receive additional inputs (e.g., yeast27 and enzymes 29) and may ferment the sugars within the fermentationslurry to produce a certain concentration of ethanol within thefermentation slurry. Fermentation process 28 may produce a certainamount of carbon dioxide (CO2) and other gases, which may be processedthrough the use of a scrubber or other suitable equipment, and/or becaptured and used as a source of solvent such as supercritical CO2 orliquid CO2 in the downstream ethanol separation phase. The main productof fermentation process 28 is beer 20, which comprises a liquidscomponent 16 and a solids component 15. Saccharification process 26 andfermentation process 28 may be performed separately or may be combinedinto a substantially integrated process.

In some embodiments, the beer 20 is then directed into a separationprocess 38 such as described in connection with FIG. 1. Here, the beer20 is contacted with solvent 23 (such as supercritical CO2 or liquidCO2) resulting in two product streams, a liquids product stream 16 and asolids product stream 15. The solids product stream 15 may be directedto an evaporation process 44 (directed to an evaporation system) toremove solvent and produce dried solids 45, whereas the liquids stream16 may be directed into a separation process 42 (directed to aseparation system) to produce ethanol 43. In some embodiments, theseparation process 42 may include one or more of: an evaporation processto remove the solvent 23 and a distillation or other process to separatewater from ethanol. In some embodiments, the solvent, which has beenreleased from the solids stream 15 and/or the liquids stream 16 may berecycled back into the system, for example for use again in theseparation process 38, and/or for example, for use in the separationprocess 42 to separate water from ethanol. In embodiments, wherein thesolvent is released from the solids stream 15 and/or liquids stream 16in gas phase, it may be directed to a compressor to be recompressed intoa supercritical fluid or liquid gas before being recycled back into thesystem.

FIG. 3 is a schematic illustration of an embodiment of a reactor 100 inwhich separation process 38 may be implemented. As shown, the reactor100 is a conduit comprising an impermeable first portion 110 that issubstantially impermeable to fermentation beer liquids separated from animpermeable second portion 120 that is also substantially impermeable tofermentation beer liquids by a permeable portion 130 that issubstantially permeable to fermentation beer liquids but not thefermentation beer solids. The permeable portion 130 includes anenclosure 140 which contains fluid flowing out of the permeable portionand directs it through a port 150 to liquid separation system (notshown) such as a distillation system.

The reactor also includes a first port 115 in the first impermeableportion 110, through which solvent enters the reactor 100, a second port125 also in the first impermeable portion 110 through which a solidsproduct stream containing solvent and beer solids exits the reactor, anda third port 145 at the other end of the reactor in the secondimpermeable portion 140 through which beer 20 is introduced into thereactor 100. In some embodiments, the reactor 100 is oriented such thatsolvent flows with the assistance of gravity and beer 20 flows againstgravity. For example, the reactor 100 may be oriented substantiallyvertically, as shown in FIG. 3.

In operation, the reactor 100 is maintained at, or brought to,conditions in which the solvent 23 is in supercritical fluid or liquidgas form. In some embodiments, wherein the solvent 23 is a liquid gas,the reactor conditions are chosen to maintain the substance in liquidform while minimizing the heat of vaporization associated withconverting the liquid to gas during the subsequent, evaporation process.Beer 20 is brought into the bottom of the reactor (the secondimpermeable portion 120 of the reactor in the exemplified embodiment)through port 145 and flows upward. The liquid component 16 of the beer20 flows out of the reactor at the impermeable portion 130 and isdirected to a separations system through port 150. The solids component15 of the beer 32 continues to flow upward past the permeable portion130 into the first impermeable portion 110, where it mixes with solvent,which is introduced into the reactor 100 (through the first impermeableportion 110 in the exemplified embodiment) through port 115. In someembodiments, wherein the solvent 23 is a lighter density fluid than thebeer 32, the solvent 23 may contribute to pushing the beer liquid 16 outthe permeable portion 130. In some embodiments, without wishing to bebound by theory, using a supercritical fluid or liquid gas as a solvent23 facilitates higher flow rates of solution through the solids 15 withlower pressure because of the reduced viscosity of the supercritical orliquid gas solvent 23 as compared to the beer liquid 16. The solidsstream 15, now mixed with solvent 23, leaves the top of the extractorthrough port 125 and is directed into an evaporation system (not shown).

In some embodiments, the evaporation system may be simply designed toinvolve decreasing pressure in the system by venting the solids streamto air. In other embodiments, the evaporation system may be designed toreduce pressure as the solids stream passes through just enough to causethe supercritical fluid or liquid gas to change to a gas phase and leavethe evaporator. In some embodiments, the now dried solids can leave theevaporator through a gas-tight lock system to be discharged at standardatmospheric conditions.

In some embodiments, the evaporation system may be designed toaccommodate a multi-stage evaporation process 44, for example to reduceor minimize the amount of energy needed to recompress the solvent, nowin gas phase, back into supercritical or liquid gas form, as compared tothe energy required to recompress gas that is formed by reducingconditions to room temperature and pressure. Designing such a process iswithin the ordinary skill in the art following the principle that thesmaller the pressure change between the supercritical form/liquid gasform and gas phase, the less energy is needed to recompress the gas backto supercritical form. By way of example, if the separation operatingpressure conditions are 1000 psi, and the supercritical fluid forms agas at 900 psi, in a first stage of the evaporation process, thepressure may be dropped to 900 psi rather than atmospheric pressure.Despite the conditions being consistent with a change from supercriticalfluid form to gas phase, some solvent may remain trapped in the solids.Accordingly, the pressure may then be lowered further to help drive outremaining gas. The number of stages (the number of times the pressure isfurther reduced) and/or the lowest pressure used for releasing gas is amatter of choice, but may be driven by economic considerations. Forexample, if the cost of increasing pressure from atmospheric pressure toa final pressure in the evaporator is less than the cost of recoveringgas at that final pressure, a person of skill may decide simply to ventgas at that final pressure rather than recover it. In some embodiments,gas released from the system may be brought to a compressor to berecompressed into supercritical fluid or liquid gas and recycled backinto the system.

In some embodiments, the (liquid stream) separation system may alsoutilize the novel solvents according to this disclosure (i.e.supercritical fluid or liquid gas solvents) to target extraction ofethanol, oil, and/or ethanol and oil from other fermentation liquidcomponents, such as water. For example, a supercritical fluid or liquidgas solvent can be chosen in which ethanol preferentially dissolves atcertain temperature and pressure conditions relative other fermentationliquid components, or in which ethanol and oil preferentially dissolveat certain temperature and pressure conditions relative otherfermentation liquid components. In some embodiments, the solvent issupercritical CO2.

In some embodiments, in operation, as the liquid product stream exitingthe separations reactor 100 passes through the (liquid stream)separations system, temperature and pressure conditions are set suchthat ethanol and oil preferentially solubilize in the solvent ascompared to water, resulting in a water phase which can be separatedfrom a product stream comprising ethanol, oil and solvent. The ethanoland oil can then be separated by changing the temperature and pressureconditions (for example by lowering the pressure) such that only ethanolis preferentially solubilized in the solvent. After removing the oil,the conditions of temperature and pressure can again be changed (forexample the pressure can be further lowered) so that ethanol mayseparate from the solvent.

In some embodiments, the separations system involves more than oneiteration (i.e. the liquid stream is solubilized in the solvent, thesolvent is removed and the product stream is thereafter repeatedlysolubilized in the solvent until a target product stream having adesired ethanol content is achieved). In some embodiments, the ethanolmay be separated from water using additional or alternative approachesknown to those of skill in the art, such as distillation.

The principles described herein wherein a novel solvent is used to drybeer solids and/or to extract ethanol, oil, and or ethanol and oil canbe implemented at other points in the fermentation process flow. Forexample, in the exemplified embodiments, beer solids are dried prior todistillation. However, in an alternative embodiment, the beer solids maybe dried using the novel solvent after the fermentation beer isdistilled, for example the extraction of dried beer solids can becarried out on whole stillage, or on the wet cake, rather than the beeritself.

As another example of a permutation within scope of this disclosure, thenovel solvent can be used to extract oil during fermentation rather thanafter fermentation (as part of the liquid product stream separationprocess). For example, a slip steam could be extracted from thefermenter to an extraction tank, which could be a continuous stirredreactor. The solvent could be brought into the tank and mixed with theslip stream. The tank could be brought to or maintained at temperatureand pressure conditions wherein the oil is preferentially soluble in thesolvent resulting in a mixture of oil and solvent (and ethanol to theextent ethanol has begun to form in the fermenter and is thereforepresent in the slip stream) as compared to water. The mixture may betransferred to a separator where conditions are changed, for example thepressure is reduced, sufficiently to cause the oil to separate outresulting in a heavy phase containing oil and a light phase containingethanol and solvent. The light phase can then be passed to anotherseparator where the conditions are changed again (for example thepressure is further lowered) resulting in separation of ethanol from thesolvent. Extraction of oil during fermentation could be carried out fora desired time period, including only initially when little ethanol hasformed, or until the bulk of the oil is extracted, or throughoutfermentation, as some examples.

In another embodiment, the solvent can be used to extract ethanol duringfermentation. The process would be similar to the oil extraction processdescribed above, except the slip stream would be exposed to conditionsof temperature and pressure in which only ethanol solubilized in thesolvent and not also the oil. Processes in which ethanol is removedduring fermentation (e.g. which enable the ethanol content to becontrolled during fermentation) may facilitate new methods offermentation in which yeasts or other organisms may be used for sugarconversion, which are not ethanol tolerant. Again, as a person of skillmay understand, although ethanol is separated from oil, it may stillinclude some water content. Accordingly, in some embodiments, theethanol stream may be subjected to additional extractions using thenovel solvent, may undergo a distillation process to separate out water,may undergo any other appropriate separation process known to those ofskill in the art to separate the water from ethanol, or combinationsthereof.

A number of embodiments have been described but a person of skillunderstands that still other embodiments are encompassed by thisdisclosure. For example, the use of the solvent to extract ethanol, oilor ethanol and oil, can be implemented anywhere there is a liquidmixture containing ethanol, oil, or ethanol and oil. As another example,extraction techniques using the novel solvents can be combined withother separation techniques. For example, oil could be extracted frombeer using the novel solvent and ethanol could be removed using anothertechnology such as mechanical separation. It will be appreciated bythose skilled in the art that changes could be made to the embodimentsdescribed above without departing from the broad inventive conceptsthereof. It is understood, therefore, that this disclosure and theinventive concepts are not limited to the particular embodimentsdisclosed, but are intended to cover modifications within the spirit andscope of the inventive concepts including as defined in the appendedclaims. Accordingly, the foregoing description of various embodimentsdoes not necessarily imply exclusion. For example, “some” embodiments or“other” embodiments may include all or part of “some”, “other,”“further,” and “certain” embodiments within the scope of this invention.

What is claimed is:
 1. A method of purifying feedstock-to-ethanolfermentation products, comprising: a. exposing a first mixture chosenfrom fermentation beer and mixtures derived therefrom to a solvent undera first set of conditions in which the solvent is in a supercriticalfluid or liquid gas form thereby generating a second mixture comprisinga subset of components of the first mixture and the solvent; b.separating the second mixture from remaining components of the firstmixture; and, c. removing the solvent from the second mixture.
 2. Amethod according to claim 1, wherein the first mixture is chosen from afermentation beer, whole stillage, and wet cake, and wherein the firstmixture comprises a solids portion and a liquids portion, generatingcomprises displacing the liquids portion from the solids portion withthe solvent, and the second mixture comprises the solids portion and thesolvent.
 3. A method according to claim 2, wherein the first mixture isa pre-distillation fermentation beer.
 4. A method according to claim 1,wherein removing comprises exposing the second mixture to a second setof conditions in which the solvent converts to a gas phase.
 5. A methodaccording to claim 3, further comprising using a separations reactor toexpose the first mixture to the solvent, wherein the separations reactorcomprises a length of walls segmented into a first length of impermeablewalls connected to a second length of impermeable walls by a length ofpermeable walls, wherein the first and second length of impermeablewalls are impermeable to fermentation liquids and the permeable wallsare permeable to fermentation liquids but impermeable to fermentationsolids; and, wherein exposing comprises: flowing the solvent into afirst end of the separations reactor through the first length ofimpermeable walls toward the length of permeable walls; flowing thefermentation beer through a second end of the separations reactorthrough the second length of impermeable walls toward the length ofpermeable walls, resulting in a fermentation solids stream exiting theseparations reactor at a first port in the in the first end of theseparations reactor and the fermentation liquids exiting the separationsreactor through the permeable length of walls.
 6. A method according toclaim 1, wherein the first set of conditions are chosen to result in atleast one of ethanol and oil solubilizing in the solvent generating asecond mixture comprising ethanol, oil or both, according to the firstset of conditions, and solvent.
 7. A method according to claim 1,wherein the fermentation beer comprises a liquids portion and a solidsportion and the first mixture comprises the liquids portion of thefermentation beer, and further wherein the first set of conditions arechosen to result in ethanol and oil present in the liquids portionsolubilizing in the solvent, and removing comprises: a. exposing thesecond mixture to a second set of conditions in which oil separates outof the second mixture resulting in a third mixture comprising ethanoland solvent; b. separating the oil from the third mixture; c. exposingthe third mixture to a third set of conditions in which ethanolseparates out of the solvent; d. exposing the solvent to a fourth set ofconditions in which the solvent converts to gas; and, e. venting thegas.
 8. A method according to claim 7, wherein the vented gas iscaptured and directed to a compressor to be recompressed intosupercritical fluid or liquid gas.
 9. A method according to claim 7,further comprising separating water from ethanol.
 10. A method accordingto claim 1, wherein the first mixture is a slip stream from a fermenter,and the first set of conditions is chosen to solubilize oil in thesolvent to generate the second mixture.
 11. A system, comprising: a. anethanol production facility for producing ethanol from a feedstock usinga fermentation process; b. a solvent in supercritical fluid or liquidgas form; and, c. a separations reactor integrated into the ethanolproduction facility, wherein the separations reactor is suitable for useat conditions supporting the solvent in a supercritical fluid or liquidgas form, or both; the separations reactor comprising: i. one or moreinputs for receiving the solvent and a first mixture chosen from afermentation beer and mixtures derived therefrom; and, ii. one or moreoutputs for removing a second mixture comprising the solvent and asubset of components of the first mixture and for removing remainingcomponents of the first mixture.
 12. A system according to claim 11,wherein: the separations reactor comprises a first impermeable portionjoined to a second impermeable portion by a third permeable portion,wherein the first impermeable portion and second impermeable portion aredefined by walls that are impermeable to fermentation liquids and thepermeable portion is defined by walls that are permeable to fermentationliquids and impermeable to fermentation solids; the one or more inputsis a first input located in the first impermeable portion forintroducing solvent into the separations reactor and a second inputlocated in the second impermeable portion for introducing fermentationbeer into the separations reactor; and the one or more outputs is afirst output located in the first impermeable portion for removing amixture comprising fermentation solids and solvent from the reactor anda second output which is the permeable walls for removing a mixturecomprising fermentation liquids and solvent from the reactor.
 13. Asystem according to claim 12, wherein the separations reactor furthercomprises and enclosure with an integral port surrounding the permeableportion to capture the mixture exiting the separations reactor at thepermeable portion and direct the mixture to a next part of the system.14. A system according to claim 12, wherein the separations reactor hasa top portion which is the first impermeable portion and a bottomportion which is the second impermeable portion and the separationsreactor is vertically-oriented such that solvent may flow assisted bygravity and fermentation beer may flow against gravity.
 15. A systemaccording to claim 13, further comprising an evaporator in fluidcommunication with the first output, and which evaporator has one ormore discharge outlets for releasing gas produced when conditions in theevaporator are set consistent with the solvent converting to a gasphase.
 16. A system according to claim 15, wherein the system furthercomprises: a compressor in fluid communication with the evaporator forrecompressing gas discharged from the evaporator; and, means forrecycling the recompressed gas back into the solids extractor.